What kind of dryer? Mine is a condenser and wouldn't heat up recently, because the empty water light was on, so that prevents the heating kicking in. Google the exact make and model - I did, and found lots of helpful advice. The water was collecting in the wrong place as the pump wasn't working. So I took the back panel off, ordered a new pump online, and fitted it. £30 instead of a new one! If I can do it, you can...and I took a photo or two of what I was taking out so I could put the new part in correctly. Good luck!
When mine broke like this it was the thermostat, I googled to get an idea of where it was on my particular model and then bought the part off eBay. On mine it was inside the drum, above the door so quite awkward to get to, but it wasn't that hard to fix.
There are only three main bits that can break on a tumble drier: the motor, the belt and the heating element.
If it still turns around, the belt and the motor are fine. This is good, because changing the belt can be a pain and the motor is the most expensive bit.
There will probably be a panel on the back of your drier that has a 'Hot' warning on it, that you can unscrew. The heater is under there. UNPLUG THE DRYER FROM THE WALL AND ONLY THEN take the panel off, and try hoovering the dust off it. If it still doesn't work, you will be able to unplug the element and get another off eBay for not much.
help i put a load of clothes in to dry yesterday- put them in for 20mins, which is usually long enough- but they came out still damp and cold It has been making a strange noise for a week but i thought it just needed a new bearing. AArrggh i rely on the drier as weather up here is rubbish, ans central heating is so expensive. hmmmm i guess ill have to call someone out to fix it.